The present invention relates to a control device for stopping an internal combustion engine and, more particularly, to a control device for the elimination of periodic oscillations between operating states of an internal combustion engine, which is being stopped.
Control devices for series injection pumps in which the control rod is brought into a stop position via an operating piston controlled with an auxiliary energy in mechanically regulated series injection pumps with key-activated stopping are already known. A hydraulic control device using the fuel pressure has been suggested. Also a pneumatic control device using excess air pressure or vacuum has been proposed to solve this problem. In addition, an electrical control device for this purpose has been suggested using electrical energy as the auxiliary energy. None of these control devices for stopping the internal combustion engine would be reliable.
If the fuel pressure is used to provide the auxiliary energy, a diesel fuel brine and filter clogging can occur at low temperatures. As in the case of fuel leakages, the pressure build-up in this case is also disturbed or even no longer producible.
The same is true for compressed air as auxiliary energy when the auxiliary energy is no longer available in sufficient quantity due to compressed air leakages, e.g. because of a pressure drop in the compressed air container over longer standing times.
A complete failure of the auxiliary energy can occur, often without warning, when power is supplied by current when a current failure occurs in the electrical lines for various reasons.
According to DE-AS 15 76 658, it is known in a control device of this type to utilize engine lubricating oil pressure as auxiliary energy for the shut-off or stopping device. In so doing, a front side of the control rod is acted upon directly by the engine lubricating oil, which is under pressure, for stopping the series injection pump and a displacement of the control rod is accordingly triggered in such a way that the latter arrives in its stopping position and the fuel feed is switched off. A magnet valve in the form of a 3/2-way valve, which is connected to the generator, is used to control this process, a relief line being connected to the magnet valve in addition to a feed and discharge pressure line.
However, a disadvantage in this arrangement consists in that the pressurized space, which is acted upon by the lubricating oil for moving the control rod into the stopping position, can be relieved for restarting only via the 3/2-valve which is costly in terms of construction. Since the 3/2-valve enables the control rod to move out into the stopping position only as a result of its operation, a current failure, which can occur e.g. because of a broken cable, can make it possible to stop at all.
Moreover, in this arrangement when the engine is stopped the holding current for the electromagnet of the magnet valve has already dropped so far at very low engine speed of the internal combustion engine, during which the generator no longer gives off sufficient voltage for operating the magnet valve, that the magnet valve closes again and the regulating path is at least partially reopened, the engine catches, restarts and does not completely stop again. This state correspond to a regulating behavior known as "hunting" and is a periodic oscillation between two unwanted operating states, so that a sure stopping of the internal combustion engine is prevented.